The present invention relates to a method for modifying the physical properties of bituminous materials and to asphalt compositions obtained therefrom. More particularly, the present invention relates to a method of producing industrial asphalts. Industrial asphalts have many uses but are particularly useful in roofing applications.
The physical properties of asphalt vary over a wide range. FIG. 1 is a softening point-penetration plot for various industrial asphalt grades. The four rectangles in FIG. 1 outline the properties of Types I-IV industrial asphalts as defined by the American Society for Testing and Materials (ASTM-D312). The plot illustrates the tremendously varying properties required of industrial asphalts for different applications. Industrial asphalts have softening points above 135 degrees Fahrenheit.
Properties of bituminous materials may be modified by such well-known treating means as solvent extraction, air-blowing and the like.
Air-blowing processes using catalysts are known in the art for making industrial asphalts. However, air-blowing processes require complex and expensive air-blowing equipment which must meet ever more stringent air pollution regulations. Furthermore, air-blowing requires long processing times on the order of hours.
U.S. Pat. No. 3,751,278 discloses a process for treating asphalts without air-blowinge using phosphoric acids having an H3PO4 equivalent of greater than 100 percent. The compositions produced by this process are directed to paving asphalts particularly useful in highway construction and maintenance. Paving asphalts usually have softening points below 135 degrees Fahrenheit and penetrations from 20 to 300 dmm at 77 degrees Fahrenheit. This patented process is particularly directed to treating asphalts to substantially increase the viscosity without a significant decrease in penetration.
U.S. Pat. No. 2,179,208 teaches a process for making asphalt which comprises air-blowing in the absence of any catalyst at a temperature of 300 to 500 degrees Fahrenheit for 1 to 30 hours followed by a second step of heating that material to a temperature greater than 300 degrees Fahrenheit with a small amount of polymerizing catalysts. The catalysts include phosphoric acid, ferric chloride, BF3, etc. Using small amounts of these catalysts, products with melting points of 140 degrees Fahrenheit or less were produced. The patent teaches that overall processing times are significantly reduced using this two-step process.
Ferric chloride is a well-known catalyst for use in the air blowing of asphalt. See, for example, U.S. Pat. Nos. 1,782,186; 2,627,498 and 2,776,933.
One object of the present invention is to produce an industrial asphalt in a simple one-step process without any prior air-blowing treatment of the bituminous material feed stock or any post air-blowing treatment of the asphalt formed.
A second object of the present invention is to provide a process for producing industrial asphalts where treatment times are very short, in the order of 5 to 25 minutes or less.
Another object of the present invention is to provide a process which can utilize as a feed, bituminous materials which heretofore could not be used in making industrial asphalts by the prior art air-blowing process without the addition of substantial amounts of lower boiling hydrocarbons.